The Myth of the Rational Market: A History of Risk, Reward, and Delusion on Wall Street

By Justin Fox

A New York Times Bestseller and Notable Book: “A rich history of the world’s most seductive investing idea.” —Bloomberg

A Library Journal Best Business Book of the Year

A lively history of ideas, The Myth of the Rational Market by former Time magazine economics columnist Justin Fox describes with insight and wit the rise and fall of the world’s most influential investing idea: the efficient markets theory. Longlisted for the Financial Times Business Book of the Year Award, The Myth of the Rational Market carries readers from the earliest days of Wall Street to the global financial crisis and Great Recession, debunking the long-held myth that the stock market is always right in the process while intelligently exploring the replacement theory of behavioral economics.

“A fascinating historical narrative, beginning with economist Irving Fisher’s paean to markets in, alas, 1929.” —Roger Lowenstein, The Washington Post

“Brilliantly tells the story of how [the finance industry’s] edifice was built—and why so few were willing to acknowledge that it was a house built on sand.” —Paul Krugman, The New York Times Book Review

“His analysis is singularly compelling and the rare business history that reads like a thriller . . . A must-read for anyone interested in the markets, our economy or government.” —Publishers Weekly (starred review)

“A valuable and highly readable history of risk and reward.” —Burton Malkiel, The Wall Street Journal

• Language: English
• Publisher: Open Road Integrated Media
• Release date: Jun 2, 2009
• ISBN: 9780061885709

Justin Fox

Justin Fox is editorial director of the Harvard Business Review Group, and a contributor to Time magazine and PBS's Nightly Business Report. Previously, he was a columnist at Time and an editor and writer at Fortune. He lives in Cambridge, Massachusetts, with his wife and son.

Book preview

THE MYTH OF THE RATIONAL MARKET

A History of Risk, Reward, and Delusion on Wall Street

JUSTIN FOX

Dedication

To Allison

Contents

Cover

Title Page

Dedication

Introduction: It had been Working So Exceptionally Well

Early Days

1. Irving Fisher Loses his Briefcase, and Then his Fortune

The first serious try to impose reason and science upon the market comes in the early decades of the twentieth century. It doesn’t work out so well.

2. A Random Walk from Fred Macaulay to Holbrook Working

Statistics and mathematics begin to find their way into the economic mainstream in the 1930s, setting the stage for big changes to come.

The Rise of the Rational Market

3. Harry Markowitz Brings Statistical Man to the Stock Market

The modern quantitative approach to investing is assembled out of equal parts poker strategy and World War II gunnery experience.

4. A Random Walk from Paul Samuelson to Paul Samuelson

The proposition that stock movements are mostly unpredictable goes from intellectual curiosity to centerpiece of an academic movement.

5. Modigliani and Miller Arrive at a Simplifying Assumption

Finance, the business school version of economics, is transformed from a field of empirical research and rules of thumb to one ruled by theory.

6. Gene Fama Makes the Best Proposition in Economics

At the University of Chicago’s Business School in the 1960s, the argument that the market is hard to outsmart grows into a conviction that it is perfect.

The Conquest of Wall Street

7. Jack Bogle Takes on the Performance Cult (and Wins)

The lesson that maybe it’s not even worth trying to beat the market makes its circuitous way into the investment business.

8. Fischer Black Chooses to Focus on the Probable

Finance scholars figure out some ways to measure and control risk. More important, they figure out how to get paid for doing so.

9. Michael Jensen Gets Corporations to Obey the Market

The efficient market meets corporate America. Hostile takeovers and lots of talk about shareholder value ensue.

The Challenge

10. Dick Thaler Gives Economic Man a Personality

Human nature begins to find its way back into economics in the 1970s, and economists begin to study how markets sometimes fail.

11. Bob Shiller Points Out the Most Remarkable Error

Some troublemaking young economists demonstrate that convincing evidence for financial market rationality is sadly lacking.

12. Beating the Market With Warren Buffett and Ed Thorp

Just because professional investors as a group can’t reliably outperform the market doesn’t mean that some professional investors can’t.

13. Alan Greenspan Stops a Random Plunge Down Wall Street

The crash of 1987 exposes big flaws in the rational finance view of risk. But a rescue by the Federal Reserve averts a full reexamination.

The Fall

14. Andrei Shleifer Moves Beyond Rabbi Economics

The efficient market’s critics triumph by showing why irrational market forces can sometimes be just as pervasive as the rational ones.

15. Mike Jensen Changes his Mind About the Corporation

The argument that financial markets should always set the priorities—for corporations and for society—loses its most important champion.

16. Gene Fama and Dick Thaler Knock Each Other Out

Where has the debate over market rationality ended up? In something more than a draw and less than a resounding victory.

Epilogue: The Anatomy of a Financial Crisis

Cast of Characters

Searchable Terms

Acknowledgments

About the Author

Afterword

A Note on Sources

Notes

Praise for The Myth of the Rational Market

Credits

Copyright

About the Publisher

INTRODUCTION

IT HAD BEEN WORKING SO EXCEPTIONALLY WELL

ON THE FOURTH THURSDAY OF October in 2008, eighty-two-year-old Alan Greenspan paid a visit to Capitol Hill to admit that he had misunderstood how the world works. Sitting at the witnesses’ table in the hearing room on the first floor of the Rayburn House Office Building, the former Federal Reserve chairman started by reading a statement that tried to explain what had gone so wrong with financial markets over the past year. After asking Greenspan a few questions, the chairman of the House Committee on Government Oversight and Reform, California Democrat Henry Waxman, summed up. In other words, he said, you found that your view of the world, your ideology, was not right. It was not working.

Precisely, replied Greenspan. That’s precisely the reason I was shocked, because I had been going for forty years or more with very considerable evidence that it was working exceptionally well.¹

During those forty years—especially the nineteen during which Greenspan was the world’s top central banker—financial markets grew to play an ever-larger and less-fettered role. The stock market boomed for most of Greenspan’s years at the Fed. Bond markets boomed too, and expanded into new territory as Wall Street whizzes took mortgage loans and auto loans and credit card debt off the balance sheets of banks and repackaged them into asset-backed securities sold to investors around the world. The most dizzying growth came in over-the-counter derivatives, custom-made financial instruments (options, futures, swaps) that tracked the movements of other financial instruments. With them, traders could insure against or bet on moves in currencies or interest rates or stocks. In recent years it had even become possible to use derivatives to insure against loans gone bad. From 1987 to 2007, the face value of over-the-counter derivatives rose from $866 billion to $454 trillion.²

As Fed chairman, Greenspan had celebrated this financialization of the global economy. These instruments enhance the ability to differentiate risk and allocate it to those investors most able and willing to take it,³ he said in 1999, referring to derivatives in particular. Greenspan had once expressed the worry, in 1996, that stock markets might be losing themselves in a frenzy of irrational exuberance. When they kept rising after that, he took the lesson that the market knew more than he did.

This was Greenspan’s ideology—and it had been widely shared in Washington and on Wall Street. Financial markets knew best. They moved capital from those who had it to those who needed it. They spread risk. They gathered and dispersed information. They regulated global economic affairs with a swiftness and decisiveness that governments couldn’t match.

AND THEN, SUDDENLY, THEY DIDN’T. The whole intellectual edifice collapsed in the summer of last year, Greenspan admitted at the October 2008 hearing.⁴ That was when the private market for U.S. mortgage securities collapsed, beginning a fitful unraveling of asset market after asset market around the world. Distrust spread. Many previously thriving credit markets shut down entirely. Bank runs—long thought to endanger only actual banks—threatened any financial institution that ran on borrowed money. After Greenspan’s successor at the Fed, Ben Bernanke, and Treasury Secretary Hank Paulson decided in September 2008 not to step in to avert such a run on Lehman Brothers, global finance virtually ceased functioning. It took a partial government takeover of the financial system—not just in the United States but in Europe—to bring back even a modicum of calm.

Greenspan struggled to explain what had gone wrong because the intellectual edifice around which he had built his thinking simply didn’t allow room for the events of the preceding fourteen months. This was the edifice of rational market theory. The best-known element of rational market theory is the efficient market hypothesis, formulated at the University of Chicago in the 1960s with reference to the U.S stock market. The belief in the so-called rational market that took hold in the years that followed, though, was about more than just stocks. It held that as more stocks, bonds, options, futures, and other financial instruments were created and traded, they would inevitably bring more rationality to economic activity. Financial markets possessed a wisdom that individuals, companies, and governments did not.

The notion that financial markets know a lot has been around as long as financial markets themselves. In 1889, stock market chronicler George Rutledge Gibson asserted that when shares become publicly known in an open market, the value which they there acquire may be regarded as the judgment of the best intelligence concerning them.⁵ Hints of this same attitude could be found in the work of early economists such as Adam Smith—and even the religious thinkers of the Middle Ages. While some medieval ecclesiastical scholars argued that lawgivers should set a just price for every good to guarantee that producers earned a living wage and consumers weren’t gouged, others, St. Thomas Aquinas among them, held that the just price was set by the market.⁶

All these early claims for the correctness and justness of market prices came with caveats—doses of realism, you could call them. George Gibson wrote that stock exchanges were prone to manias and panics and called for the regulation of bucket shops that urged customers to speculative excess.⁷ Adam Smith thought corporations with widely dispersed ownership—the shares of which are what make stock markets go—were abominations. Thomas Aquinas made no claim that the market price was always right, just that it was hard to come up with a fairer alternative.

The twentieth-century version of rational market theory was different—both more careful and more extreme. It started with the observation that the movements of stock prices were random, and could not be predicted on the basis of past movements. This observation was followed by the claim that it was impossible to predict stock prices on the basis of any publicly available information (such as earnings, balance sheet data, and articles in the newspaper). From those starting points—both of which were, it turned out later, not entirely correct—flowed the conviction that stock prices were in some fundamental sense right.

Most of the scholars who backed this hypothesis early on didn’t mean for it to be taken as a literal description of reality. It was a scientific construct, a model for understanding, for testing and engineering new tools. All scientific models are oversimplifications. The important test is whether they’re useful. This particular oversimplification was undeniably useful, so useful that it took on a life of its own. As it traveled from college campuses in Cambridge, Massachusetts, and Chicago in the 1960s to Wall Street, Washington, and the boardrooms of the nation’s corporations, the rational market hypothesis strengthened and lost nuance.

It was a powerful idea, helping to inspire the first index funds, the investment approach called modern portfolio theory, the risk-adjusted performance measures that shape the money management business, the corporate creed of shareholder value, the rise of derivatives, and the hands-off approach to financial regulation that prevailed in the United States from the 1970s on.

In some aspects the story of the rational market hypothesis parallels and is intertwined with the widely chronicled rebirth of pro-free-market ideology after World War II. But rational market finance was not at heart a political movement. It was a scientific one, an imposing of the midcentury fervor for rational, mathematical, statistical decision making upon financial markets. This endeavor was far from an unmitigated disaster. It represented, in many ways, the forward march of progress. But much was lost, most importantly the understanding—common among successful investors but absent from several decades of finance scholarship—that the market is a devilish thing. It is far too devilish to be captured by a single simple theory of behavior, and certainly not by a theory that allowed for nothing but calm rationality as far as the eye could see.

As far back as the 1970s, dissident economists and finance scholars began to question this rational market theory, to expose its theoretical inconsistencies and lack of empirical backing. By the end of the century they had knocked away most of its underpinnings. Yet there was no convincing replacement, so the rational market continued to inform public debate, government decision making, and private investment policy well into the first decade of the twenty-first century—right up to the market collapse of 2008.

This book offers no grand new theory of how markets truly behave. It is instead a history of the rise and fall of the old theory—the rational market theory. It is a history of ideas, not a biography, or even a collection of biographies. But it is full of characters—most of them economists and finance professors—who were actors in many of the great dramas of the twentieth century, from 1920s boom to 1930s Depression to war and then peace and prosperity, then 1960s boom and 1970s bust and so on. These characters weren’t the lead actors, for the most part. But they were crucial to the plot. (A reference list of key players can be found on backmatter.)

The ideas of economists and political philosophers, both when they are right and when they are wrong, are more powerful than is commonly understood, wrote John Maynard Keynes, who plays a supporting role in the story to follow. Indeed, the world is ruled by little else. Practical men, who believe themselves to be quite exempt from any intellectual influences, are usually the slaves of some defunct economist.

The defunct economist with whom this tale begins is Keynes’s contemporary Irving Fisher.

EARLY DAYS

CHAPTER 1

IRVING FISHER LOSES HIS BRIEFCASE, AND THEN HIS FORTUNE

The first serious try to impose reason and science upon the market comes in the early decades of the twentieth century. It doesn’t work out so well.

It is 1905. A well-dressed man in his late thirties talks intently into a pay phone at Grand Central Depot in New York. Between his legs is a leather valise. The doors of the phone booth are open, and a thief makes off with the bag. It is, given what we know of its owner, of excellent quality. Finding a willing buyer will not be a problem.

The contents of the valise are another matter. Stuffed inside is an almost-completed manuscript that brings together economics, probability theory, and real-world business practice in ways never seen before. It is part economics treatise, part primer on what rational, scientific stock market investing ought to look like. It is a glimpse into Wall Street’s distant future.

THAT SCIENCE AND REASON MIGHT be applied to the stock exchange was still a radical notion in 1905. Wall Street and its captains ran the stock market, and they and their friends either owned or controlled the speculative pools, recalled one journalist of the time. "The speculative public hardly had a chance. The right stockholders knew when to buy and sell. The others groped."¹

Times, though, were changing. Good information about stocks and bonds was getting easier for the speculative public to obtain. Corporations had become too big and too interested in respectability to be controlled by just a few cronies. The dark corners of Wall Street were being illuminated. Maybe the investing world was ready for a more scientific approach.

The stolen manuscript was never seen again, but its author, Yale University economics professor Irving Fisher, had a habit of overcoming setbacks that might cause a lesser (or more realistic) individual to despair. As he prepared to set off for college in 1884, his father died of tuberculosis, leaving the undergraduate to support his mother and younger siblings. Just as his academic career began to take off in the late 1890s, Fisher himself came down with TB, which incapacitated him for years. In 1904, finally healthy and working again, he watched as fire consumed the house just north of Yale’s campus where he lived with his wife and two children.

And then the theft of his manuscript. Afterward, inured by then to disaster, Fisher went right back to work. He resolved always to close the door when he entered a phone booth, and he rewrote his book, this time making copies of each chapter as he went along. Published in 1906 as The Nature of Capital and Income, it cemented his international reputation among economists. It became, as one biographer wrote, one of the principal building blocks of all present-day economic theory.²

Its impact on Wall Street was less immediately obvious. Stockbrokers and speculators did not rush out to buy the book. There’s no evidence that investors began making probability calculations before they bought stocks, as Fisher recommended. But Fisher was at least as persistent as he was lacking in street smarts. His ideas began to have some impact in his lifetime, and after his death in 1947, they took off.

Books directly or indirectly descended from Fisher’s work now adorn the desks of hedge fund managers, pension consultants, financial advisers, and do-it-yourself investors. The increasingly dominant quantitative side of the financial world—that strange wonderland of portfolio optimization software, enhanced indexing, asset allocators, credit default swaps, betas, alphas, and model-derived valuations—is a territory where Professor Fisher would feel intellectually right at home. He is perhaps not the father, but certainly a father of modern Wall Street.

Hardly anyone calls him that, though. Economists honor Fisher for his theoretical breakthroughs, but outside the discipline his chief claim to lasting fame is the horrendous stock market advice he proffered in the late 1920s. Read almost any history of the years leading up to the great crash of October 1929, and the famous Professor Fisher serves as a sort of idiot Greek chorus, popping up every few pages to assert that stock prices had reached a permanently high plateau. He wasn’t just talking the talk. Fisher blew his entire fortune (acquired through marriage, then increased through entrepreneurial success) in the bear market of late 1929 and the early 1930s.

Fisher’s two historical personas—buffoon of the great crash and architect of financial modernity—are not as alien to each other as they might at first appear. In the early years of the twentieth century Fisher outlined a course of rational, scientific behavior for stock market players. In the late 1920s, blinded in part by his own spectacular financial success, he became convinced that America’s masses of speculators and investors (not to mention its central bankers) were in fact following his advice. Nothing, therefore, could go wrong.

Irving Fisher had succumbed to the myth of the rational market. It is a myth of great power—one that, much of the time, explains reality pretty well. But it is nonetheless a myth, an oversimplification that, when taken too literally, can lead to all sorts of trouble. Fisher was just the first in a line of distinguished scholars who saw reason and scientific order in the market and made fools of themselves on the basis of this conviction. Most of the others came along much later, though. Irving Fisher was ahead of his time.

HE WAS NOT, HOWEVER, ALONE in his advanced thoughts about financial markets. In Paris, mathematics student Louis Bachelier studied the price fluctuations on the Paris Bourse (exchange) in a similar spirit. The result was a doctoral thesis that, when unearthed more than half a century after its completion in 1900, would help to relaunch the study of financial markets.

Bachelier undertook his investigation at a time when scientists had begun to embrace the idea that while there could be no absolute certainty about anything, uncertainty itself could be a powerful tool. Instead of trying to track down the cause of every last jiggling of a molecule or movement of a planet, one could simply assume that the causes were many and randomness the result. It is thanks to chance—that is to say, thanks to our ignorance, that we can arrive at conclusions, wrote the great French mathematician and physicist Henri Poincaré in 1908.³

The greatest tool for building knowledge upon such ignorance was what was called the Gaussian distribution (after German stargazer and mathematician Carl Friedrich Gauss), the normal distribution, or simply the bell curve. A Gaussian array of numbers can be adequately described by invoking only the mean (i.e., the top of the bell) and what in the waning years of the nineteenth century came to be known as the standard deviation (the width of the bell). As scientists of the time were discovering, the bell curve popped up again and again in measurements of natural phenomena. The temptation to apply it to human endeavor was for some irresistible.

Bachelier used the assumptions of the bell curve to depict price movements on the Paris exchange. He began with the insight that the mathematical expectation of the speculator is zero.⁴ That is, the gains and losses of all the buyers and sellers on the exchange must by definition cancel each other out. This isn’t strictly true—stocks and bonds have delivered positive returns over time—but as a logical framework for investing or speculating, Bachelier’s diagnosis remains unsurpassed. The average investor cannot beat the market. The average investor is the market.

From this beginning, Bachelier realized, it is possible to study mathematically the static state of the market at a given instant, i.e., to establish the law of probability of price changes consistent with the market at that instant.⁵ It was a view of the market as a game of chance, like roulette or dice. And just as games of chance can be described mathematically (and had been since the 1500s), Bachelier sketched the probabilities of the exchange.

His work was so innovative that when Albert Einstein employed similar mathematical tools five years later to describe the random motion of tiny particles suspended in a fluid or a gas—called Brownian motion, after the botanist who first noted it—he helped lay the foundations of nuclear physics. But while physicists, building upon Einstein’s work, were putting together atomic bombs by the 1940s, practical application of Bachelier’s insights would not emerge until the 1970s.

This is not simply a tale of ignored genius. There was a major limitation to Bachelier’s work, of which he was well aware. His teacher, Henri Poincaré, made sure of that. While he celebrated the use of the bell curve in the physical sciences, Poincaré thought caution needed to be exercised in applying it to human behavior. The Gaussian distribution, or the bell curve, is the product of countless random and independent causes. When men are brought together, Poincaré wrote, they no longer decide by chance and independently of each other, but react upon one another. Many causes come into action, they trouble the men and draw them this way and that, but there is one thing they cannot destroy, the habits they have of Panurge’s sheep.⁶

Panurge, a character from Rabelais’s satirical Gargantua and Pantagruel novels, got a flock of sheep to jump off a ship by throwing the lead ram overboard. In his examination of the Paris Bourse, Bachelier eluded the stampeding sheep only by limiting the application of his formulas. One might fear that the author has exaggerated the applicability of Probability Theory as has often been done, Poincaré wrote in his grading report on the thesis. Fortunately, this is not the case.

Bachelier contrived to see no more than an instant into the future, assuming that price changes in that instant would be unpredictable in direction but predictably small. That was as far as math could get him. The probability dependent on future events, he conceded, is impossible to predict in a mathematical manner. It is precisely this probability, he acknowledged, that most interests the speculator. He analyzes causes which could influence a rise or a fall of market values or the amplitude of market fluctuations. His inductions are absolutely personal, since his counterpart in a transaction necessarily has the opposite opinion.⁷

That was that. Bachelier went on to a modestly successful career as a math professor, and published a well-received popular treatise on games, chance, and risk (Le jeu, la chance et le hasard). When he died in 1946, one year before Irving Fisher, no one on the trading floor was making use of his ideas. His colleagues, meanwhile, were nonplussed by his interest in markets. On a bibliography of Bachelier’s writings found in the files of the great French mathematician Paul Lévy is scrawled the complaint, Too much on finance!⁸

IRVING FISHER WAS ABLE TO go where Bachelier did not because he had more than just mathematics and probability theory at his disposal. He was an economist. He was able to go where other economists did not because he, unlike all but a handful of them at the time, was a mathematician. And he was able to do something tangible with his insights because he was a wealthy resident of a country where, in the early decades of the twentieth century, financial markets were just beginning to grow into the vast bazaars that would steer the economy for the rest of the century and beyond.

At Yale, where he graduated first in the class of 1888 even while supporting his family with tutoring jobs and academic prizes, Fisher majored in mathematics. But he also took five courses in economics and sociology with the legendary William Graham Sumner. Despite personal coldness and a crisp, dogmatic classroom manner, Sumner had a wider following than any teacher in Yale’s history, wrote one historian. He was also, in this estimation, the most vigorous and influential social Darwinist in America.⁹

In its most primitive form, social Darwinism was the belief that Charles Darwin’s theory of evolution applied not just to plants and animals but to human affairs, and that the nineteenth-century rise of industrial capitalism in the United States and Great Britain was a Darwinian matter of the survival of the fittest. Sumner’s version was gloomier and more sophisticated than that. He worried that those who aimed to improve society (social doctors, he called them) would inevitably screw it up. They do not understand that all parts of society hold together, he wrote in 1883 in one of a series of Harper’s articles later bundled into the classic tract What the Social Classes Owe to Each Other, and that forces which are set into action act and react throughout the whole organism, until an equilibrium is produced by a readjustment of all interests and rights.¹⁰

The concept of equilibrium, in which competing influences balance each other out, lends itself naturally to mathematical treatment (all it takes is an equal sign) and was crucial to the early development of chemistry and physics. Hints of it had already appeared in economics—Scotsman Adam Smith’s notion of an invisible hand steering selfish individuals toward societally beneficial results was the most famous example¹¹—but attempts to build a unified theory of economics around it had foundered upon the imprecision of the field.

Economists were long stuck, for example, on the crucial question of what gave a product value. Was it the labor that went into producing it? Its abundance or scarcity? Its usefulness? Some combination of all three? In the 1870s, scholars in Austria, England, and Switzerland hit simultaneously upon an elegant answer, and a new era in economics—the neoclassical era, as it is called—began. Value always depends upon degree of utility, wrote one of the neoclassical pioneers, Englishman William Stanley Jevons, and labour has no connection with the matter, except through utility. If we can readily manufacture a great quantity of some article, our want of that article will be almost completely satisfied, so that its degree of utility and consequently its value will fall.¹²

From this basic building block of utility, one could conceivably build a coherent mathematical theory of economic equilibrium—which is what Jevons and a few of the other early neoclassical theorists set out to do. Yale’s Sumner knew of these developments, and was enthusiastic about them. To get up to speed, he even hired a math professor to tutor him.¹³ But he struggled, and when Fisher returned to the Yale campus in autumn 1888 for graduate study in mathematics, Sumner took the young man aside and urged him to examine the new mathematical economics.

Thus was launched the economics career of Irving Fisher. For his doctoral thesis he devised the most sophisticated mathematical treatment yet of economic equilibrium, and he also designed and built a contraption of interconnected water-filled cisterns that he described as the physical analogue of the ideal economic market.¹⁴ Many decades later, economist Paul Samuelson judged this work to be the greatest doctoral dissertation in economics ever written.¹⁵ It launched Fisher into a leading role among the world’s still-sparse ranks of mathematical economists.

After getting his doctorate in 1893, Fisher married a daughter of the wealthiest family in his Rhode Island hometown. Her industrialist father (founder of a company that became one of the building blocks of Allied Chemical) paid for a year-long voyage through Europe for the newlyweds while building them a mansion just north of the Yale campus, where Fisher already had an offer to teach math and economics. On his European adventure Fisher met most of the founding fathers of neoclassical economics, and sat in on a few Poincaré lectures on probability in Paris. On his return, he brought his economic knowledge to bear on a matter of public policy for the first time.

The American Civil War of the 1860s had been followed by a decades-long decline in prices that left America’s farmers feeling deeply victimized, a conviction that only hardened during the depression of the mid-1890s. A farmer who borrowed money to buy seed in 1895, when corn sold for as much as fifty cents a bushel, couldn’t make his loan payments a year later when the price dropped to twenty-one cents.¹⁶ The explanation for the deflation was that dollars were redeemable in gold, and there wasn’t enough gold to go around. The less gold there was, the fewer dollars were in circulation. When fewer dollars chase the same goods, prices drop. The farmers were being crucified, presidential hopeful William Jennings Bryan said in his famous acceptance speech at the 1896 Democratic Convention, on a cross of gold.

In Fisher’s ideal economic market, the complaints of Bryan and the farmers were beside the point. Markets automatically adjusted to changing price levels. Multitudes of trade journals and investors’ reviews have their sole reason for existence in supplying data on which to base prediction, Fisher wrote in 1896. Every chance for gain is eagerly watched. An active and intelligent speculation is constantly going on, which, so far as it does not consist of fictitious and gambling transactions, performs a well-known and provident function for society. Is it reasonable to believe that foresight, which is the general rule, has an exception as applied to falling or rising prices?¹⁷ As farmers and their bankers could foresee that prices would drop, Fisher’s reasoning went, interest rates on loans would drop too—so farmers wouldn’t be any worse off.

THIS ASSUMPTION THAT PEOPLE COULD see clearly into the future was crucial to making equilibrium economics work. It was also crucially problematic. You regard men as infinitely selfish and infinitely farsighted, Henri Poincaré wrote to mathematical economist Léon Walras in 1901. Infinite selfishness may perhaps be admitted in a first approximation, Poincaré allowed. But the assumption of infinite farsightedness may call for some reservations.¹⁸

The events that followed the publication of Fisher’s gold standard argument were a textbook demonstration of the limits to foresight. Gold discoveries in Alaska and South Africa, coupled with the development of a new process for separating gold from ore, set the world on a decades-long inflationary path that no one had foreseen. The way people dealt with rising prices—or, more to the point, failed to deal with them—convinced Fisher that Bryan had been on to something in 1896.

In the midst of this reexamination, in 1898, a dire personal crisis arose for Fisher: the onset of tuberculosis, the same disease that had killed his father fourteen years before. Only after three years spent in clinics in Southern California, upstate New York, and Colorado Springs—and three more operating at half speed back in New Haven—did the young professor recover. He came away from the experience with an obsession for good health and a near-messianic fervor to better the world before his death. Fisher became a leading prohibitionist, coauthor of a bestselling hygiene textbook, a disciple of the corn-flakes-prescribing Dr. Kellogg of Battle Creek, an early backer of the League of Nations, and a prominent advocate of eugenics.

This last cause has since gotten a deservedly bad rap. But the intent was to improve the world, and the same could be said of Fisher’s post-TB economics. Fisher became what his mentor William Graham Sumner would have mocked as a social doctor, but he never strayed far from the bounds of neoclassical theory. His work on monetary policy led him to spend decades educating Americans about inflation and deflation and promoting government policies to keep prices stable. His take on the stock market exhibited a similar spirit.

This spirit was evident in The Nature of Capital and Income, the book Fisher lost at Grand Central in 1905 and rewrote in 1906. He kept it almost equation free to appeal to a broad readership, but his mathematical sensibility still permeated it. If we take the history of the prices of stocks and bonds, Fisher wrote, we shall find it chiefly to consist of a record of changing estimates of futurity, due to what is called chance. This was similar to Bachelier’s depiction of Brownian motion at the Paris exchange. A half century later the concept was dubbed the random walk hypothesis, occasioning all manner of academic excitement. But the experiences of the previous decade had turned Fisher into enough of a realist that he immediately backpedaled from his bold statement. Stock and bond price movements weren’t entirely random, he continued:

Were it true that each individual speculator made up his mind independently of every other as to the future course of events, the errors of some would probably be offset by those of others. But, as a matter of fact, the mistakes of the common herd are usually in the same direction. Like sheep, they all follow a single leader.

Ah, those sheep again. But Fisher, ever the civic improver, hoped to make investors less ovine by getting them to use economics and probability theory. The value of any investment, he wrote, is the income it will produce. Money in the future is not worth as much as money today. People are impatient, and they must be compensated for the opportunity cost of not investing in some other productive endeavor. The current value, then, is the expected income stream discounted by a measure of people’s preference for having the money now rather than later, also known as interest.

In 1906, sophisticated investors already consulted bond tables that listed the present, or discounted, value of interest payments to be received in the future. The calculations behind these tables dated all the way back to the fourteenth century.¹⁹ What was radically new in Fisher’s work was his proposal to incorporate uncertainty into the equation—enabling investors to use the present-value formula to price not just bonds but stocks. At the time, investing in corporate shares was a new and suspect pursuit. Limited liability corporations, in which shareholders partake in the profits but are not liable for the company’s debts if it goes under, had only recently become common in the United States and Great Britain. Bonds, along with real estate, were the chief means of investment. Stocks were for pure speculation.

To Fisher, this distinction made no economic sense. The fact that bond interest was guaranteed while stock dividends were not was only a difference of degree. Bond issuers could go bankrupt, after all, and inflation could eat into the value of even the safest bond. Yes, there was more uncertainty in valuing stocks than in bonds. But so what? And while Bachelier had distinguished between the fixed probability of games of chance (which could be rendered mathematically) and the personal probability involved in peering into an uncertain future (which, he said, could not), Fisher saw the difference as one of degree. Even the objective probability of dice throwing and coin flipping wasn’t a sure thing, he argued. You could flip a fair coin a million times and it was possible, albeit highly improbable, that it would come up heads every time.

Fisher proposed that investors count the dividends they expected a stock to pay out in the future, and then plug that income estimate into a formula of the sort used to value bonds. This riskless value could then be adjusted by adding in an estimate of the chance that dividends might be larger than expected and subtracting the chance they might be smaller. This value could then be multiplied by a measure of caution (nine-tenths, Fisher suggested, without further explanation) to come up with a price.

It was all a lot of work, Fisher acknowledged. But that’s how economic progress was achieved. Wrote Fisher:

There was a time when business men did not use bond tables, when they did not calculate cost sheets, and even when life insurance was contracted for in scornful disregard of any mortality tables. Just as these slipshod methods have been displaced by the work of expert accountants and actuaries, so should the mere guessing about future income conditions be replaced by making use of the modern statistical applications of probability.

Uncertainty could not be banished, Fisher was saying. But with enough data and the right mindset it could be tamed. The data were being churned out in abundance by 1906. The mindset took a bit longer.

AS NEW INDUSTRIAL GIANTS SUCH as Standard Oil, U.S. Steel, and General Electric grew to prominence in the decades before and after the turn of the century, their hankering for respectability and capital led them to disclose ever more about their finances. Data factories such as Moody’s, Fitch, and Standard Statistics arose to assemble and disseminate this information. The Wall Street Journal was born in 1883, and soon afterward cofounder Charles Dow began compiling the stock price averages that for the first time allowed investors to discuss how the market was doing. The profession of stock market statistician was born—the number-crunching precursor of today’s securities analyst.

The leaders of this information revolution were not interested in exploring the bounds of uncertainty and probability as Fisher advised. Instead, they hoped their number crunching could give them something more valuable—the ability to see into the future and forecast the cycles of the market.

That there were cycles seemed obvious to most. Securities markets as we understand them today (continuously operating, indoor exchanges) developed in the late 1700s as European governments began selling bonds on a regular basis, mainly to finance wars. There had been famous market manias and panics before—tulip mania in 1630s Holland, and in the early 1700s the Mississippi Bubble in France and the South Sea Bubble in England. It was only in the 1800s that observers began to see a certain regularity in them. Near-clockwork regularity, it seemed. In England there were market panics in 1804–5, 1815, 1825, 1836, 1847, and 1857.

A famous early explanation for these cycles